lkml.org 
[lkml]   [2012]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/3] audit: fix refcounting in audit-tree
Date
From: Miklos Szeredi <mszeredi@suse.cz>

Refcounting of fsnotify_mark in audit tree is broken. E.g:

refcount
create_chunk
alloc_chunk 1
fsnotify_add_mark 2

untag_chunk
fsnotify_get_mark 3
fsnotify_destroy_mark
audit_tree_freeing_mark 2
fsnotify_put_mark 1
fsnotify_put_mark 0
via destroy_list
fsnotify_mark_destroy -1

This was reported by various people as triggering Oops when stopping auditd.

We could just remove the put_mark from audit_tree_freeing_mark() but that would
break freeing via inode destruction. So this patch simply omits a put_mark
after calling destroy_mark or adds a get_mark before.

The additional get_mark is necessary where there's no other put_mark after
fsnotify_destroy_mark() since it assumes that the caller is holding a reference
(or the inode is keeping the mark pinned, not the case here AFAICS).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reported-by: Valentin Avram <aval13@gmail.com>
Reported-by: Peter Moody <pmoody@google.com>
Acked-by: Eric Paris <eparis@redhat.com>
CC: stable@vger.kernel.org
---
kernel/audit_tree.c | 5 ++---
1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 69a5851..2b2ffff 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -250,7 +250,6 @@ static void untag_chunk(struct node *p)
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
fsnotify_destroy_mark(entry);
- fsnotify_put_mark(entry);
goto out;
}

@@ -293,7 +292,6 @@ static void untag_chunk(struct node *p)
spin_unlock(&hash_lock);
spin_unlock(&entry->lock);
fsnotify_destroy_mark(entry);
- fsnotify_put_mark(entry);
goto out;

Fallback:
@@ -332,6 +330,7 @@ static int create_chunk(struct inode *inode, struct audit_tree *tree)
spin_unlock(&hash_lock);
chunk->dead = 1;
spin_unlock(&entry->lock);
+ fsnotify_get_mark(entry);
fsnotify_destroy_mark(entry);
fsnotify_put_mark(entry);
return 0;
@@ -412,6 +411,7 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
spin_unlock(&chunk_entry->lock);
spin_unlock(&old_entry->lock);

+ fsnotify_get_mark(chunk_entry);
fsnotify_destroy_mark(chunk_entry);

fsnotify_put_mark(chunk_entry);
@@ -445,7 +445,6 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
spin_unlock(&old_entry->lock);
fsnotify_destroy_mark(old_entry);
fsnotify_put_mark(old_entry); /* pair to fsnotify_find mark_entry */
- fsnotify_put_mark(old_entry); /* and kill it */
return 0;
}

--
1.7.7


\
 
 \ /
  Last update: 2012-08-21 22:01    [W:0.038 / U:0.048 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site